1. Field of the Invention
The present invention relates to conveyor feeder systems for supplying products to packaging machines at appropriate spacings and positions.
2. Description of the Prior Art
In commercial baking operations, products such as cookies emerge from a baking machine in a sequential but generally randomly spaced manner. Before they can be packaged by a wrapping machine, however, the cookies must be spaced from one another by predetermined distances, and positioned at precise locations. The wrapping machine generally has its own feed conveyor with a plurality of dividers known as dogs positioned at spaced locations thereon. The area between dogs is known as a flite, while the distance between the dogs is characterized as a flite length. The packaging machine will function properly only if one cookie is positioned between the dogs in each flite. Conveyor feeder systems receive the randomly spaced products from the baking machine, space the products at flite lengths with respect to one another, and synchronize their positions with the flites before transferring them to the wrapper conveyor.
Known conveyor feeder systems of the assignee of the present invention include a plurality of correction conveyors positioned upstream from the wrapper conveyor, and a conveyor drive system. The drive system includes a system processor, and a drive motor and associated command generator for each correction conveyor. The correction conveyors are initially driven at a one-to-one velocity ratio with respect to the wrapper conveyor. Sensors coupled to the system processor detect cookies on the correction conveyors and dogs on the wrapper conveyor. Each time a cookie is detected on one of the conveyors, the phase or positional error between the cookie and its desired position on a flite is computed by the system processor and downloaded to the command generator associated with the correction conveyor on which the cookie is located. The command generator then implements an error correction using a multi-segmented velocity profile switching technique to increase or decrease the speed of the correction conveyor with respect to that of the wrapper conveyor.
All error corrections are made over a constant command distance which is generally equal to the distance the cookie travels on the correction conveyor before being transferred to a subsequent conveyor. The error correction velocity of the correction conveyor is constant over the command distance, and is controlled by velocity clock values generated by the command generator and applied to a servo translator and amplifier system associated with the drive motor. The command generator includes a binary rate multiplier which produces pulse trains having frequencies determined as a function of the velocity clock values. Velocity of the drive motor and correction conveyor is determined by the frequency of the pulse train. Data representative of conveyor positions and distances of travel is stored in RAM of the command generator.
Feeder systems also typically include an accumulator or backlog conveyor which receives the randomly spaced cookies from the production machine. The velocity of the accumulator conveyor is controlled as a function of the velocity of the wrapper conveyor and the rate at which cookies are being received from the production machine. The accumulator conveyor backlogs or bunches up the cookies so they can be correctly positioned by the correction conveyors. In noncontacting conveyor systems the accumulator conveyor must be run at a sufficient speed to prevent sequential cookies from touching one another.
The system described above is optimized by controlling the velocity of the wrapper conveyor as a function of the rate of products produced by the production machine. Ideally, the feeder system will place one cookie in each flite. In practice, faulty wraps for which either zero or two cookies are placed in the same flite occur on occasion. In addition to associated waste of package and cookies, faulty wraps can jam the wrapper.
A variety of conveyor feeder systems for this and other applications also disclosed generally in the following U.S. Pat. Nos.: 3,335,841, Klingel et al.; 3,485,339, Miller et al.; 4,135,346, Rebsamen; 4,172,347, Nitz; 4,197,935, Aterianus et al.; 4,355,712, Bruno; 4,514,963, Bruno; 4,604,704, Eaves et al.; 4,653,630, Bravin; 4,640,408, Eaves.
The Klingel et al. U.S. Pat. No. 3,335,841 discloses the use of a control conveyor associated with a feed conveyor. The control conveyor is driven at a different speed than the feed conveyor and carries a plurality of driving members which are spaced at equal distances from one another. The driving members drop downward and engage the articles, thereby shifting their position as required for proper transfer into a conveying receptacle of the packaging machine.
The Miller et al. U.S. Pat. No. 3,485,339 discloses a system for spacing articles of different lengths. Articles are sequentially transferred from an entry conveyor to a spacing conveyor, approach conveyor, weight conveyor and exit conveyor. Motion of the spacing and approach conveyors is controlled by spacing control circuitry in response to the presence of articles optically detected thereon so as to position only one box on the weighing conveyor while weighing operations are being performed.
The Rebsamen U.S. Pat. No. 4,135,346 discloses apparatus for controlling the speed of operation of a packaging machine so as to assure a sufficient supply of objects to the machine while preventing undue accumulation. A signal processor receives signals from several sensors which indicate the passage of objects past selected points, and generates motor control signals as a function thereof.
The Nitz U.S. Pat. No. 4,172,347 discloses an electronic control system for controlling the sequence of operations of products moving on an indexing conveyor.
The Aterianus et al. U.S. Pat. No. 4,197,935 discloses a system for feeding spaced articles through a processing machine. The supplied articles are sequentially transferred to an accumulating conveyor, metering conveyor, infeed conveyor and wrapper. The infeed conveyor and metering conveyor are driven from a variable speed drive and are synchronized with the wrapper. An electrical circuit controls the operation of the various conveyors as a function of articles sensed thereon.
The Bruno U.S. Pat. No. 4,355,712 discloses apparatus for feeding products to a work station. A first conveyor receives a longitudinal row of products which are touching one another. A second conveyor receives products from the first conveyor and is driven at a speed greater than that of the first conveyor. Products on the second conveyor are detected by sensors. A control system controls the speed of the first conveyor in such a manner that products on the second conveyor are received at the same point in working cycles of a work station.
The Bruno U.S. Pat. No. 4,514,963 discloses a system for regulating the feed of articles to a wrapping machine. Sensors are arranged to provide signals indicative of the degree of any deviation of each article from a correct position in phase with the wrapping machine. A control circuit corrects the speed of the conveyor as a function of the detected deviation.
The Eaves et al. U.S. Pat. No. 4,604,704 discloses a high-speed microprocessor-controlled branch conveyor. The conveyor receives serial products from a supply conveyor, and adjustably conveys the products so as to establish a predetermined spacing therebetween. The products are transferred from supporting belts to the individual flites of a pusher member containing conveyor. Product flow is synchronized relative to an infeed conveyor to a wrapping station.
The Bravin U.S. Pat. No. 4,653,630 discloses a system for controlling the transfer of articles from a first conveyor belt to predetermined locations on a second conveyor belt. Signals representative of the position of the second belt are stored whenever an article arrives on the first belt. An error signal is generated and used to control the speed of the upstream belt and correct the article position with respect to the downstream belt. At each adjustment of the speed of the upstream belt a digital feedback signal is generated to progressively annul the error signal while the article position is being corrected.
The Eaves U.S. Pat. No. 4,640,408 discloses a feeder with automatic zoned product timing correction. The position of products on a separation belt relative to the position of a transfer conveyor flite is determined as being within one of five possible zones. Associated with each zone is a predetermined velocity change with respect to the separation belt which is required to move the product to the correct positional relationship.
It is evident that there is a continuing need for improved conveyor feeder systems. The system should be capable of accurately positioning the desired number of products in each and every flite of the wrapper. The system must also be capable of operating at high rates of speed to accommodate efficient production and wrapping machines. A noncontacting feeder system having these characteristics would be especially desirable.